Reusable, polystyrene-resin-supported, palladium-catalyzed, atom-efficient cross-coupling reaction of aryl halides with triarylbismuths

Article abstract of DOI:10.1002/ejoc.200901210

A rapid, atom-efficient, cross-coupling reaction of triarylbis- muths with aryl bromides or aryl iodides was reported, and the reaction involves the use of a catalytic amount of polystyrene-supported palladium in the presence of KF as base in DMSO at 105 0C in an open atmosphere. All three aryl groups of the triarylbismuths participated in the reaction and produced polyfunctional biaryls in excellent yields. The polymeric catalyst can be easily separated from the reaction mixture and reused more than 10 times without showing any obvious decrease in activity.

Full text of DOI:10.1002/ejoc.200901210

SHORT COMMUNICATION
DOI: 10.1002/ejoc.200901210
Reusable, Polystyrene-Resin-Supported, Palladium-Catalyzed, Atom-Efficient
Cross-Coupling Reaction of Aryl Halides with Triarylbismuths
Wen-Jun Zhou,[a] Ke-Hu Wang,[a] Jin-Xian Wang,*[a,b] and Dan-Feng Huang[a]
Keywords: Cross-coupling / Bismuth / Halides / Heterogeneous catalysis / Supported catalysts / Palladium
A rapid, atom-efficient, cross-coupling reaction of triarylbis-
muths with aryl bromides or aryl iodides was reported, and
the reaction involves the use of a catalytic amount of polysty-
rene-supported palladium in the presence of KF as base in
DMSO at 105 °C in an open atmosphere. All three aryl
groups of the triarylbismuths participated in the reaction and
produced polyfunctional biaryls in excellent yields. The poly-
meric catalyst can be easily separated from the reaction mix-
ture and reused more than 10 times without showing any
obvious decrease in activity.
reactions, organobismuth compounds have not been well
studied.[9] Organobismuth compounds are normally non-
toxic and potentially useful candidates for environmentally
benign reagents, which is a major contemporary concern in
the chemistry community.[10] Recently, some reactions in-
volving organobismuth for C–C bond formation based on
Pd-catalyzed cross-coupling have been reported.[11] Triaryl-
bismuths, unlike organoboron, organotin, and other rea-
gents, can react with three equivalents of an electrophilic
reagent.[12] Among the limited successful examples for the
construction of C–C bonds, long reaction times and harsh
reaction conditions (such as under the protection of N2 or
under anhydrous and anaerobic conditions) were indispens-
able to accomplish the reaction. Furthermore, Pd-
(PPh3)4,[11b,12b] Pd(OAc)2,[12a] or PdCl2[12c] was used for the
coupling reaction. These homogeneous catalysts are expens-
ive or air sensitive, which limits their industrial applications
and it is difficult to recycle and reuse these homogeneous
catalysts due to their low stability toward oxidation.[13]
These results stimulated us to pursue further research on
these kinds of reactions. Herein, we report a highly efficient
polystyrene-supported PdII-catalyzed protocol for an atom-
efficient coupling of triarylbismuths with aryl iodides or
aryl bromides in an open atmosphere. The methodology re-
ported here has the following advantages: atom economical,
short reaction time, broad substrate scope, simplicity of op-
eration, as well as an easily recyclable catalyst with high
efficiency.
Introduction
The palladium-catalyzed cross-coupling reaction of elec-
trophilic reagents with organometallic reagents is one of the
most important synthetic methods for the construction of
C–C bonds,[1] especially in the synthesis of biaryl com-
pounds, which are important structural substructures in nu-
merous natural products, polymers, agrochemicals, and
pharmaceutical intermediates.[2] During the past decades,
many palladium complexes have been used as homogeneous
systems in these reactions, but most of them are expensive
and air sensitive. Although these homogeneous catalysts al-
ways exhibit better activity and selectivity than hetero-
geneous ones,[3] heterogeneous catalysts have many advan-
tages over homogeneous catalysts in industrial processes,
such as recycling and lower cost. Thus, many polymer-sup-
ported[4] and inorganic solid-supported[5] (e.g., carbon, sol–
gel, clays, and metal oxides) palladium catalysts have been
reported. Among these supporters, cross-linked polystyrene
resins,[6] which can bear different functional groups, provide
a suitable supporter. Since the successful use of polystyrene-
bound palladium catalysts in Suzuki cross-coupling reac-
tions was reported,[7] cross-linked polystyrene supported
palladium catalysts have been widely used in organic chem-
istry reactions.[8]
Up to the present, although various organometallic com-
pounds such as organotin, organoboron, and organozinc
compounds have been successfully utilized in cross-coupling
[a] Institute of Chemistry, Department of Chemistry, Northwest
Normal University,
967 An Ning Road (E.), Lanzhou 730070, Republic of China
Fax: +86-931-776-8159
Results and Discussion
E-mail: wangjx@nwnu.edu.cn
The polystyrene-supported PdII catalyst with Pd/P ratio
of 1:1 was prepared by a procedure described previously.[8a]
In our initial efforts, we screened the cross-coupling reactiv-
ity of iodobenzene as a representative example by treating
[b] State Key Laboratory of Applied Organic Chemistry, Lanzhou
University,
Lanzhou 730000, Republic of China
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.200901210.
416
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 416–419

Reusable, Polystyrene-Resin-Supported Palladium Catalyst
it with BiPh3 and by using the polystyrene-supported PdII Table 1. Optimized conditions for the coupling of iodobenzene with
triphenylbismuth.[a]
catalyst; we optimized the conditions in terms of solvent,
base, and temperature. As shown in Table 1, solvents such
as water, dichloromethane, acetonitrile, ethanol, PEG-400,
ionic liquids, or dimethylformamide (DMF) provided poor
or moderate yield of biphenyl (Table 1, Entries 1–8), and
Entry
Base (mmol)
Solvent
T
[°C]
Time
[h]
Yield
[%][b]
dimethyl sulfoxide (DMSO) was found to be the suitable
solvent for the cross-coupling reaction (Table 1, Entry 9). In
addition, the reactions carried out in the presence of dif-
ferent bases in DMSO revealed KF as a suitable base, giv-
ing 87% cross-coupling conversion (Table 1, Entry 9).
Other bases including Na2CO3, K2CO3, K3PO4, KHCO3,
NaHCO3, Et3N, Al2O3, NaOH, and KOH provided poor
conversion (Table 1, Entries 10–17). Further study on this
reaction by varying the equivalents of KF revealed that
3.0 equivalents of base are necessary to obtain high yields
of the cross-coupling products (Table 1, Entries 18–21).
Furthermore, lowering or elevating the reaction tempera-
ture had no positive effect (Table 1, Entries 22–25). It is
noteworthy that control reactions carried out without base
(Table 1, Entry 26) or without the palladium catalyst
(Table 1, Entry 27) delivered no cross-coupling product, in-
dicating that the base and the catalyst are necessary for the
cross-coupling reaction.
Strikingly, the cross-coupling reaction carried out in the
presence of KF in DMSO with polystyrene-supported pal-
ladium catalyst (corresponding to 0.01 equiv. Pd with re-
spect to BiPh3) at 105 °C provided the highest cross-cou-
pling conversion (Table 1, Entry 19). Furthermore, the
atom efficiency of triphenylbismuth, for which all three
phenyl groups efficiently coupled with 3 equiv. of electro-
philic coupling partner, was thoroughly established.
1
2
3
4
5
6
7
8
KF (3.5)
KF (3.5)
KF (3.5)
KF (3.5)
KF (3.5)
KF (3.5)
KF (3.5)
KF (3.5)
KF (3.5)
H2O
H2O
CH2Cl2
CH3CN
EtOH
PEG 400
[Bmim]PF6
DMF
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
105
105
105
105
105
105
105
105
105
105
105
105
105
105
105
105
105
105
105
105
105
115
110
100
90
24
12
5
10
10
2
36
2
0.25
0.5
1
2
0.5
1
1
5
7
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
24
0
51[c]
66
55
65
64
35
80
87
81
84
59
78
75
35
16
18
80
94
86
78
88
91
90
80
0
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
K2CO3(3.5)
K3PO4(3.5)
KHCO3 (3.5)
NaHCO3 (3.5)
Et3N (3.5)
Al2O3 (3.5)
NaOH (3.5)
KOH (3.5)
KF (4.0)
KF (3.0)
KF (2.5)
KF (2.0)
KF (3.0)
KF (3.0)
KF (3.0)
KF (3.0)
None
105
105
KF (3.0)
24
0[d]
[a] Reaction conditions: Iodobenzene (1.0 mmol), Ph3Bi
(0.34 mmol), solvent (3 mL), base, PS-supported PdII catalyst (cor-
responding to 0.01 equiv. Pd with respect to BiPh3), stirring for the
appropriate time. [b] Isolated yield. [c] 0.3 mmol TBAB (tetrabu-
tylammonium bromide) was used. [d] Control reaction carried out
without Pd catalyst.
Subsequently, we investigated the cross-coupling reaction
of various triarylbismuths with a variety of electronically
diverse aryl iodides. The reaction of various substituted aryl
iodides with different triarylbismuths was found to be fast
and efficient, furnishing good to high yields of the cross-
coupling biphenyls in a short reaction time. As shown in
Table 2, the reaction of both iodobenzene (Table 2, En- yields of the functionalized biphenyls (Table 3, Entries 1–4).
tries 1–4) and electron-withdrawing aryl iodides (Table 2, However, the cross-coupling of 1-bromo-4-chlorobenzene
Entries 5–14) afforded good to high yields of the cross-cou- gave moderate yields of products (Table 3, Entries 5 and 6).
pling products with different triarylbismuths. In particular, Furthermore, bromobenzene substituted with electron-do-
1-chloro-2-iodobenzene, which has some discernible steric nating 4-methoxy and 4-methyl groups reacted inefficiently
encumbrance, afforded the corresponding products in mod- and gave poor yields of the corresponding cross-coupled
erate yields (Table 2, Entries 15–18). Further studies indi- products (Table 3, Entries 8 and 9). Notably, electron-do-
cated that the reactions of electron-donating 1-iodo-4-meth- nating substrates, which are known to show poor reactivity
oxybenzene furnished moderate yields of the products in this type of reaction, showed moderate reactivity with
(Table 2, Entries 21 and 22). Also, it can be conducted from triarylbismuths.
Table 2 that the reactivity of a range of triarylbismuths in
the cross-coupling reaction was unaffected by a change in ported PdII catalyst were investigated on the model cou-
the electronics of the aryl rings in the triarylbismuths. pling reactions of iodobenzene with Ph3Bi in the presence
The reusability and efficiency of the polystyrene-sup-
To further elaborate the general reactivity of the present of KF in DMSO at 105 °C (Table 4). When the reaction
protocol with other electrophilic coupling reagents, we was finished, the catalyst was recycled by filtering from the
undertook the cross-coupling study with functionalized aryl reaction mixture and washing with acetone (3ϫ5 mL). Af-
bromides and the results are listed in Table 3. The reaction ter this step, the recycled catalyst was subjected to a second
of 4-bromoacetophenone, 1-bromo-4-nitrobenzene, 4-bro- run by charging with the same substrates (iodobenzene,
mobenzaldehyde, and 4-bromobenzonitrile as substrates Ph3Bi, DMSO, and KF). As shown in Table 4, high recycla-
with electron-withdrawing substituents furnished excellent ble efficiency (the average isolated yield is 92% for 11 con-
Eur. J. Org. Chem. 2010, 416–419
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
417

W.-J. Zhou, K.-H. Wang, J.-X. Wang, D.-F. Huang
Table 4. Recycling of polymer-supported PdII catalyst.[a]
SHORT COMMUNICATION
Table 2. Cross-coupling of aryl iodides with triarylbismuths.[a]
Entry
PS-supported PdII
Yield [%][b]
1
2
3
4
5
6
7
8
fresh
94
93
92
94
92
91
94
92
93
92
90
recycle 1
recycle 2
recycle 3
recycle 4
recycle 5
recycle 6
recycle 7
recycle 8
recycle 9
recycle 10
Entry
R1
R2
Time [min]
Yield [%][b]
1
2
3
4
5
6
7
8
H
H
H
H
H
4-Cl
4-CH3
4-OCH3
H
4-Cl
4-F
4-CH3
4-OCH3
H
4-Cl
4-F
15
15
15
15
15
30
20
20
20
20
30
20
20
20
20
30
30
30
40
45
50
120
94
88
85
83
96
80
82
91
89
92
82
80
92
90
73
75
78
78
80
77
58
55
9
10
11
4-NO2
4-NO2
4-NO2
4-NO2
4-NO2
3-NO2
3-NO2
3-NO2
3-NO2
3-NO2
2-Cl
2-Cl
2-Cl
2-Cl
3-CH3
3-CH3
4-OCH3
4-OCH3
[a] Reaction conditions: Iodobenzene (1.0 mmol), Ph3Bi
(0.34 mmol), DMSO (3 mL), KF (3.0 mmol), PS-supported PdII
catalyst (corresponding to 0.01 equiv. Pd with respect to BiPh3),
stirring at 105 °C for 15 min. [b] Isolated yield.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
4-CH3
4-OCH3
H
Conclusions
4-F
4-CH3
4-OCH3
4-CH3
4-OCH3
H
In conclusion, we have disclosed an efficient methodol-
ogy for the synthesis of biaryl compounds that involves the
cross-coupling of triarylbismuths with aryl bromides and
aryl iodides catalyzed by polystyrene-supported palladium.
The present protocol is highly efficient, as three equivalents
of the aryl halide reacts with one equivalent of the triaryl-
bismuth cleanly to provide a high yield of the cross-cou-
pling product in short reaction time. In addition, the poly-
styrene-supported PdII catalyst can be easily recycled, and
the efficiency of reusability of the catalyst for the coupling
reactions did not decrease much over 10 runs.
4-Cl
[a] Reaction conditions: aryl iodide (1.0 mmol), Ar3Bi (0.34 mmol),
DMSO (3 mL), KF (3.0 mmol), PS-supported PdII catalyst (corre-
sponding to 0.01 equiv. Pd with respect to BiAr3), stirring at 105 °C
for the appropriate time. All products were characterized by melt-
ing point, IR, 1H NMR, and 13C NMR spectroscopy, and MS.
[b] Isolated yield.
Table 3. Cross-coupling of aryl iodides with triarylbismuths.[a]
Experimental Section
General Procedure for the Cross-Coupling Reactions of Ar3Bi with
Aryl Halides: To a round-bottomed flask charged with a mixture
of KF (3.0 mmol), PS-supported PdII (corresponding to 1 mol-%
palladium), and DMSO (3 mL) was added the aryl halide
(1.0 mmol) and Ar3Bi (0.34 mmol). The mixture was stirred at an
oil bath temperature of 105 °C for the indicated time. After comple-
tion of the reaction as indicated by TLC, the mixture was cooled.
Ethyl acetate (10 mL) and 1  HCl (10 mL) were added, and the
mixture was then filtered and the polymer catalyst was recycled by
washing with acetone (3ϫ5 mL). The residue was extracted with
ethyl acetate (3ϫ10 mL), and the combined ethyl acetate extract
was washed with saturated NaCl, dried with anhydrous MgSO4,
filtered, and concentrated. The product was recrystallized from
95% ethanol or purified by column chromatography on silica gel
(petroleum ether/ethyl acetate, 40:1) to give the analytically pure
product.
Entry
R1
R2
Time [min]
Yield [%][b]
1
2
3
4
5
6
7
8
9
4-COCH3
4-NO2
4-CHO
4-CN
4-Cl
4-Cl
H
4-OMe
4-CH3
H
H
H
H
H
4-Cl
H
H
30
30
30
40
50
120
60
120
120
91
93
90
92
76
70
65
43
56
H
[a] Reaction conditions: aryl bromide (1.0 mmol), Ar3Bi
(0.34 mmol), DMSO (3 mL), KF (3.0 mmol), PS-supported PdII
catalyst (corresponding to 0.01 equiv. Pd with respect to BiAr3),
stirring at 105 °C for the appropriate time. All products were char-
acterized by melting point, IR, 1H NMR, and 13C NMR spec-
troscopy, and MS. [b] Isolated yield.
PS-Supported PdII Catalyst Recycling Procedure: The recycled cata-
lyst was subjected to a second run of cross-coupling reaction by
charging with the same substrates (iodobenzene, Ph3Bi, DMSO,
and KF) without further addition of PS-supported PdII. The pro-
cedure is the same as that above.
secutive runs) of the catalyst was obtained, which demon-
strates the practical recyclability of this catalyst and its po-
tential use in large-scale processes.
Supporting Information (see footnote on the first page of this arti-
cle): Experimental procedures, characterization data and copies of
1
the original H NMR and 13C NMR spectra of compounds 1–28.
418
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Eur. J. Org. Chem. 2010, 416–419

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Acknowledgments
The work was supported by the Natural Science Foundation of
China (Grant 20272047, 20572086), the Gansu Natural Science
Foundation of China (0308RJZA-100), and Key Laboratory of
Eco-Environment-Related Polymer Material (Northwest Normal
University), Ministry of Education of China.
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Received: October 23, 2009
Published Online: December 14, 2009
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